Solved 12v power consumption usb satnav

I need to substitute a 12v battery for a 12v usb cigarette lighter adaptor to power my satnav, as my car only has 6v electrics. If I wire a cig lighter outlet direct to a small sealed 12 battery in the glovebox, what size battery do I need to run a satnav on 12v for say 8 hours? I would recharge the battery overnight using a mains 12v charger connected to the battery via the cig lighter socket.Thanks, Patrick

A small 12 v Motor Cycle battery will do the job or a battery designed for a UPS. You can get 9Ah battery that will fit nicely in a glove box. A 9Ah battery will provide 9 AMps for one hour or 1 amp for 9 hours. As the SatNav is unlikely to draw more than 500 Ma this will provide power for up to 18 hours.

You could even gt a 4Ah battery but that would be leaving little in reserve.

Rather than installing a bulky 12V battery in the glovebox I'd investigate a 6V/12V transformer so you could step up the ciggy lighter socket to 12V. No battery recharge issues then. http://www.jaycar.com.au/productVie...

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